Solid porous, coated oxidizer, method of preparation and novel propellant compositions

ABSTRACT

A rocket propellant composition having an exceptionally high burning rate may be prepared by incorporating therein an oxidizing salt which comprises at least in part an ammonium salt characterized by a porous structure.

Unite States atent 1 1 Lista SOLID POROUS, COATED OXIDIZER,

METHOD OF PREPARATION AND NOVEL PROPELLANT COMPOSITIONS [75] Inventor:Edwin L. Lista, Roseville, Calif.

[73] Assignee: Aerojet General Corporation,

Elmonte, Calif.

22 Filed: Aug. 30, 1966 21 Appl.N0.:577,571

[52] U.S. Cl 149/7, 149/2, 149/19.1, l49/l9.4, l49/19.5, 149/l9.8,149/19.9, 149/l9.91, l49/l9.93

UNITED STATES PATENTS 2,969,638 l/l96l Sammons 60/219 Aug. 20, 19743,103,457 9/1963 Grossman 149/7 X 3,260,631 7/1966 Witz et a1. l 149/73,279,965 10/1966 de Brancion 149/7 X 3,287,189 11/1966 Wilson et al149/7 X Primary Examiner-Benjarnin Padgett Attorney, Agent, or Fir m--E.O. Ansell, C.

Jacobs [5 7 ABSTRACT A rocket propellant composition having anexceptionally high buming rate may be prepared by incorporating thereinan oxidizing salt which comprises at least in part an ammonium saltcharacterized by a porous structure.

39 Claims, No Drawings SOLID POROUS, COATED OXIDIZER, METHOD OFPREPARATION AND NOVEL PROPELLANT COMPOSTTIONS This invention relates toan improved solid oxidizer and to a method for its preparation and to anovel, rapid burning solid projectile or propellant compositron.

Solid propellant rocket motors in their early development were primarilyemployed in tactical, intermediate range and intercontinental ballisticmissiles. For these applications the propellant characteristicallypossessed a moderate burning rate which is adequate for the productionof the necessary thrust. Later, it became necessary to provide a solidpropellant rocket motor for use in the interception of incomingballistic missiles. To be successful for the latter application, anantimissile missile must be capable of rising very rapidly from theground upon receiving directions from a computer and proceeding to apoint of interception, sufficiently distant from the ground so that theincoming war heads may be destroyed without endangering the underlyingland mass. In order that this may be accomplished, the solid propellantemployed in the anti-missile missile must be capable of rapidlyproducing a large thrust. To achieve the required high acceleration, thepropellant must possess a high burning rate.

It has been proposed heretofore to incorporate elongated metalconductors or staples in the propellant composition to obtain highburning rates. The use of metal staples accelerates the burning rate ofthe propellant composition to a considerable degree; however, theincrease in burning rate which may be obtained is less than is sometimesdesired and in addition the use of the longitudinal or other irregularshaped metal conductors results in troublesome propellant compoundingproblems. Solid propellant compositions incorporating metal conductorsfrequently evidence an anistropy of the burning rate.

It is a principle object of this invention to provide a solid propellantcomposition which possesses a sufficiently high burning rate to besuitable for use in an anti-missile missile.

It is a further object of this invention to provide an improved solidoxidizer and a method for its production.

It is another object of this invention to provide a solid propellantcomposition characterized by a uniform burning rate in all directionsthroughout the propellant.

These and other objects of the invention will be apparent from thedetailed description which follows.

It has now been found that a solid propellant composition of a high anduniform burning rate may be prepared by incorporating therein anoxidizing salt which comprises at least in part a particulate ammoniuminorganic salt characterized by a porous structure. The porous ammoniumsalt is present in an amount effective to significantly increase theburning rate of the propellant composition and while it may totallydisplace the non-porous salt in some applications, it is usuallyprovided as a minor portion of the oxidizing salt, typically beingpresent in an amount in excess of 1 percent and less than 50 percent,preferably from about 7 to about 28 percent by weight of the totaloxidizing salt.

The porous ammonium inorganic salt particles are generally spherical andusually have an average particle diameter within the range of 5 to 4000microns. Characteristically the average particle diameter for ammoniumsalt crystals to be used in a propellant composition will be within themore narrow range of 5 to 250 microns.

The particulate porous ammonium inorganic salt is characterized by voidsthroughout and has generally a cubicle crystal structure. In a preferredembodiment, the porous salt is provided with a coating over the exteriorsurface thereof. The coating serves to substantially block theexteriorly-opening pores and may be formed of various materials capableof serving in this role. Typically, the coating will be formed of anorganic polymeric material, the preferred coating composition being analkylene imine adduct of divinyl benzene.

The preferred ammonium salt for use in the invention is ammoniumperchlorate, although other ammonium oxidizing salts such as ammoniumchromate, ammonium permanganate, ammonium nitrate, ammonium chlorate andthe like may be employed.

The effectiveness of the porous ammonium salt in increasing propellantburning rate is believed to be due to its grossly different physicalstructure from the normal ammonium oxidizing salts rather then tochanges in chemical nature. The particulate porous ammonium salt withinthe propellant composition provide areas where the burning rate isobviously considerably faster then in the propellant matrix and it isthought that the voids within the porous ammonium salt particles play animportant role. Characteristically, the porous ammonium perchlorate ofthe invention or other porous ammonium salt has an individual particledensity within the range of about 1.2 to 1.75 grams per cubiccentimeter, and preferably about 1.35 to about 1.65 grams per cubiccentimeter. The porous salt possess a bulk or packing density generallywithin the range of about 0.6 to 1.0 grams per cubic centimeter, andpreferably about 0.75 to about 0.9 grams per cubic centimeter. 1n thelatter density determination, the porous ammonium salt particles arepoured into a cylinder and the cylinder vibrated until the compositionacquires a constant bulk density.

The porous ammonium oxidizing salt of the invention is prepared byheating the ammonium perchlorate or other ammonium salt to effect apartial decomposition and a change from an orthorhombic crystalstructure to a cubicle structure. While the heating may be conducted atvarious different temperatures, for example, in the range of about C toabout 400C. Typically in the instance of ammonium perchlorate the saltis exposed to a temperature in the range of 180 to 350C, preferablywithin the range of 240 to 280C for a period of time to achieve a weightloss within the range of about 20 to about 35 percent. Heating resultsin an evolution of gas, leaving a residue which is entirely ammoniumperchlorate and crystals which have become porous. The curve of percentweight loss versus time consists of an induction period during which nosignificant weight loss occurs, followed by an acceleratory periodduring which the weight loss increases, and a deceleratory period duringwhich the weight rate decreases. When employing a temperature in therange of about 200 to 280C, the decomposition of the ammoniumperchlorate levels off after approximately 30 percent decomposition. Ithas been found that changes in particle size of the ammonium perchloratedo not appreciably effect the induction or acceleration periods butaffect the deceleratory period with smaller particles decomposing fasterthen large particles. It has been demonstrated that decomposition may beachieved either in air at atmospheric pressure or in a partial vacuum orin an inert atmosphere. In the instance of decomposition in air atatmospheric pressure the weight loss levels off at approximately 32percent.

A particularly important characteristic of partially decomposedparticulate ammonium salt, as it relates to its use as a component infast-burning propellants, is the porosity of the crystals.Photomicrographs of heated ammonium perchlorate clearly reveal theporosity. An individual particle or crystal decomposes initially only atthe surface but eventually throughout the crystal, apparently alongintermosaic boundries. Microscopic studies show that two types of poresare obtained, one type of pore being sealed inside the crystal and theother type connected with the surface by tunnels.

In a preferred manner of preparing the porous ammonium salt, thedecomposition is achieved by heating, for example, thin layers of about0.3 inch thick of the ammonium salt at 260C (in the instance of ammoniumperchlorate) for about 30 minutes in a vented oven. The porous productis then cooled to ambient temperature and degassed in a vacuum for aperiod of time, typically for 24 hours, adequate to remove residualdecomposition products. It will be appreciated that the thickness of thesalt layer may vary but will generally be less then one inch andpreferably less then one-half inch. The porous product is then storedunder dry nitrogen or other suitable dry conditions, prior to use, toprevent recrystallization and healing of the pores which would occur ifthe porous product were stored under moist conditions.

The porous ammonium perchlorate or other ammonium salt from the heatingoperation may be incorporated without further processing into the highburning rate propellant composition; including other applications, suchas explosives, ammunition, and stop-start propellant motors. However, inthe preferred embodiment the porous salt is coated to accomplish asubstantially complete closing of the exteriorly-opening pores. Theuncoated porous ammonium salt may be satisfactorily incorporated in thepropellant composition providing mixing is accomplished at atmosphericpressure. A composition mixed at atmospheric pressure will have a highburning rate; however, where the mixing is accomplished under vacuumwith the uncoated ammonium perchlorate, the mix will generally go dry.The dry condition under subsequent microscopic examination has beenshown to be due to an absorption of liquid ingredients into the tunnelpores of the porous structure. The absorption occuring under a vacuummixing may be avoided by first coating the porous ammonium salt with acompatible material. The coating which is generally an organic polymerwill comprise typically from about 3 to about 8 percent, generally lessthen percent of the weight of the ammonium salt.

The improvement in propellant burning rate is believed to beattributable to a void mechanism. The voids or pores created in theammonium crystals contain gasses generally at or near atmosphericpressure. During burning of the propellant, the high pressure of theadvancing flame front reaches the porous ammonium salt and hotcombustion gasses press into the interior of the porous salt crystal,accomplishing an ignition of the whole volume of the crystal and therebybringing about almost instantaneous combustion of the ammonium salts.

While the uncoated porous ammonium salt provides a significant increaseof propellant burning rate its results are less certain and additionallythe propellant mixing process is more difficult. In one controlled test,a porous ammonium perchlorate containing propellant compositon evidenceda burning rate of 3.4 inches per second, at 2,000 psi in contrast to aburning rate of 6.0 inches per second for a coated ammonium perchloratepropellant composition while a propellant composition containing noporous ammonium perchlorate but a like quantity of normal ammoniumperchlorate exhibited a burning rate of 1.7 inches per second. Theporous ammonium perchlorate incorporated in the coated and uncoatedexamples comprised approximately 28 percent of the total weight of theammonium perchlorate oxidizing salt. It has been noted that porousammonium perchlorate prepared from larger crystal sizes of particulateammonium perchlorate produces a stronger effect than that prepared fromsmaller sized particles of the oxidizers. For example, porous ammoniumperchlorate obtained from a particularly large particle size ammoniumperchlorate (approximately 2,500 microns) gave burning rates of 8.2inches per second at 2,000 ps1.

Various procedures and compositions may be employed to coat the porousammonium salt. A preferred procedure involves the use of a solution ofethylene imine adduct of divinyl benzene in hexane or other hydrocarbonor chlorinated hydrocarbons. The ethylene imine adduct is extracted fromsolution onto the surface of the porous ammonium salt and therehomopolymerizes to form a coating over the salt crystal. The ammoniumperchlorate or other ammonium salt catalyzes the homopolymerization ofthe alkylene imine adducts of divinyl benzene. The coating seals theouter pores of the porous ammonium salt crystal and prevents the latterpores from filling up with binder material during the mixing of thepropellant composition. The coating also improves the physicalproperties and castability of the propellant. Other lower alkylene imineadducts of divinyl benzene including propylene imine, butylene iminehave been investigated and found to be suitable. Various hydrocarbonsolvents may be used in the place of hexane or along with the hexaneincluding an hydroxy-terminated polybutadiene.

Hydroxy-terminated polybutadiene and other functionalterminatedpolybutadienes in the presence of a suitable catalyst such as normalbutyl ferrocene may be used for forming a coating for the porousammonium salt crystals. However, the polybutadiene materials are highlyviscous and difficult for this reason to use. It has been found possibleto modify the imine adduct polymer by incorporating a small amount ofhydroxypolybutadiene in the hydrocarbon solution. In one coatingprocedure, an excess of a 10 percent solution of the alkylene imineadduct of divinyl benzene in hexane is permitted to stand with theporous ammonium salt at room temperature for approximately 12 hours withan occasional agitation. The hexane is then decanted and the coatedporous ammonium salt washed with additional fresh hexane. Thereafter,the washed material is dried in a thin layer at a moderately elevatedtemperature, for example, 50C 72C. In the second procedure, a 5 percentsolution of the alkylene imine adduct of divinyl benzene in hexane isadded to the ammonium salt and the mixture tumbled in a rotary dryer ata moderately elevated temperature, for example 57 60 for 24 hours orthereabout. The hexane is then removed under vacuum.

In a presently preferred method of coating the porous ammoniumperchlorate, an alkylene imine adduct of divinyl benzene, preferably theethylene imine adduct, is placed in a one to one solution of hexane orheptane. 400 grams of porous ammonium perchlorate or other ammonium saltis placed in a slurry of 288 grams of hexane or heptane. The hexanesolution of the alkylene imine adduct is added slowly with stirring tothe ammonium perchlorate slurry. Mixing is continued for at least 2hours with the temperature being maintained at 60C. The excess liquid isdecanted and the coated porous ammonium perchlorate is dried at atemperature in the range of 60 70C for about 16 to 24 hours. In stillanother approach grams of the ethylene imine adduct or other alkyleneadduct of divinyl benzene is added to approximately 288 grams of hexaneand thoroughly mixed. 400 grams of porous ammonium perchlorate or otherporous salt is slowly added to the solution with constant stirring.Mixing continues for 20 hours at a temperature of approximately 20C. Theexcess liquid is decanted and the coated particles dried in an oven at70C for 16 to 24 hours.

It is contemplated that the porous ammonium salt of the invention ineither its coated or uncoated form may be incorporated in variouspropellant compositions. In some instances it may be desirable to usethe porous salt along with metal staples to obtain further increase inburning rate. Additionally, it is contemplated that various conventionalburning rate catalysts such as copper chromite or normal butyl ferrocenemay be used in varying amounts, for example, from about 0.01 to 6percent by weight of the total propellant in conjunction with the porousammonium salt. The propellants may also contain from about 1 to about 20percent by weight of powdered metals such as aluminum. Various knownbinders or fuels may be employed in combination with the porous ammoniumsalt oxidizing agent. Propellants of this invention can be convenientlyignited by a conventional igniter, for example, the igniter disclosed inAssignees US. Pat. No. 3,000,312, issued Sept. 19, 1961.

A preferred class of binders for use in the rapid burning propellants ofthe present invention are the reaction products of afunctional-terminated polydiolefin of the formula:

I z N P wherein Z is oxygen or sulfur; and R and R are hydrogen or loweralkyl such as methyl, ethyl and pentyl;

wherein R is a trivalent organic radical of the formula:

and R and R is hydrogen or lower alkyl of from 1 to about 4 carbons; and

wherein A is alkylene, preferably lower alkylene of from 1 to about 12carbons, and R R R and R are hydrogen or lower alkyl of from 1 to about4 carbons. Normally, the aziridinyl curing agent is employed in anamount from 1 to about 40 parts per parts of the functionally-terminatedpolydiolefin. The preferred polydiolefin of the above formula ispolybutadiene or polyisoprene having a molecular weight of from about400 to about 5,000, a viscosity at 77F of from about 5 to about 500poise, and is carboxy-terminated (Y COOI-I).

Typical aziridinyl curing agents within the scope of the foregoingformula include: tris(N-l 2-butylene )trimesamide, tri(2-methyl-3-n-butyll -aziridinyl )phosphine oxide,tri(2-ethyl-3-octadecyl- 1-aziridinyl)phosphine oxide, tri(2-methyl-3-cyclopentyl- I -aziridinyl )phosphine oxide, tri(2-methyl-3-benzyll -aziridinyl )phosphine oxide, tri( l-aziridinyl)phosphine sulfide, tri(Z-methyl-1-azinidinyl)phosphine sulfide,tri(Z-eicosyl-1-aziridinyl)phosphine sulfide, and tri(2-methyl-3-cyclohexyll -aziridinyl)phosphine sulfide.

The polyurethane binders which can be used in my propellants areprepared by reacting a compound having two or more active hydrogencontaining groups capable of polymerizing with an isocyanate asdetermined by the Zerewitinoff method, with an organic compound havingas the sole reacting groups, two or more isocyanate or isothiocyanategroups. The active hydrogen containing groups are preferably hydroxyl orthiol.

It will be apparent that, where more than two active hydrogen,isocyanate, or isothiocyanate groups are present in any of thepolyurethane reactants, the structure of the polyurethane binder willcontain at least some cross-linking. Where bifunctional reactants, suchas dihydroxy compounds and diisocyanates are employed to produce thepolyurethane binders for our novel propellants, it is necessary to alsoemploy a cross-linking" agent to provide a product having a cross-linkedstructure. Compounds suitable as crosslinking agents for thepolyurethane binders are those compounds having as the sole reactinggroups at least three groups polymerizable with active hydrogen orisocyanate groups.

Examples of compounds which we have found to be particularly suitable ascross-linking agents are 1,2,6hexanetriol; methylenebis-(orthochloroaniline); monohydroxyethyl trihydroxypropylethylenediamine; N,N,N, N-tetrakis (2-hydroxypropyl) ethylenediamine;triethanolamine; and trimethylolpropane.

A wide variety of polyurethane binders for the propellants of thisinvention can be prepared by varying the starting materials. Thesepolyurethane binders are disclosed in greater details in Assigneesco-pending applications Ser. No. 829,180 and Ser. No. 829,182, bothfiled July 23, 1959.

The preferred diisocyanate compounds are saturated or unsaturated;aliphatic or aromatic; open or closed chain; and substituted or not begroups substantially unreactive with isocyanate or hydroxyl groups suchas ketone or ether groups. Diisocyanate compounds such as tetramethylenediisocyanate, decamethylene diisocyanate; m-phenylene diisocyanate;diphenylene-4,4- diisocyanate; 2,4-tolylene diisocyanate; S-nitraza 1,3-pentane diisocyanate; duren diisocyanate; and 2,6- tolylene diiscyanateare particularly suitable as reactants for the preparation ofpolyurethane binders.

The preferred hydroxy starting materials for the polyurethane bindersare dihydroxy compounds having the general formula:

where R is a divalent organic radical, such as alkylene or arylene. Thehydroxy groups on the above compounds can be of any type suitable forthe urethane reaction with isocyanate groups such as, for example,alcohol or phenolic hydroxy groups.

Other dihydroxy compounds suitable for the polyurethane reaction of thisinvention are polyesters such as those obtained from the reaction of adihydric alcohol such as ethylene glycol, with a dicarboxylic acid suchas succinic acid. The polyesters most suitable for purposes of thisinvention are those having a molecular weight from about 1000 to about2,500.

In addition to the polyesters, polyethers such as polyethylene etherglycols, polypropylene ether glycols, other polyalkylene ether glycols,and mixtures or copolymers thereof having molecular weights of fromabout 200 to about l0,000 can be utilized as dihydroxy reactants of thepolyurethane reaction of this invention.

Other binders which may be employed in my novel propellants includeresinous binders such as rubbers, polysulfides, and rubber-polysulfidemixtures.

Examples of rubber binders which can be employed within the scope ofthis invention are polyisobutylene, butyl rubber, butadiene-styrenecopolymers such as Buna-S, a butadiene-acrylonitrile copolymer such asBuna-N, highly polymerized vinyl alcohols in a plasticized state such aspolyvinyl alcohol and polychloroprene. The polysulfides suitable assolid propellant binders are exemplified by polyalkylene sulfides suchas that resulting from the condensation of ethylene dichloride andsodium tetrasulfide. A more complete description of rubber andpolysulfide propellant binders can be found in Assignees US. Pat. No.3,012,866, issued Dec. 12, 1961.

Still other examples of polymeric organic material suitable as bindersare phenol-aldehyde resins, polyester resins, acrylate resins andpolyalkylene resins.

The so-called polyester resins suitable for use as propellant bindersare formed by reacting a polyhydric alcohol with a polycarboxylic acidand copolymerizing therewith a monomeric ethylenically unsaturatedcompound, compatible with the resin. To permit heteropolymerizationbetween the polyester and ethylenically unsaturated components, thepolyesters are provided with some unsaturation through the incorporationtherein of unsaturated polycarboxylic acid or anhydride and/orunsaturated polyhydric alcohol.

Saturated polycarboxylic acids useful in compounding the polyesterresins are, for example, the aliphatic dibasic acids, including oxalic,malonic, succinic, glutaric, adipic, pimelic, sebacic and azelic. Theunsaturated acids useful as the acidic components in forming polyesterresins are maleic acid, fumaric acid, citraconic acid and mesaconicacid, itaconic acid. The anhydrides such as itaconic anhydrides andphthalic anhydride may also be used to supply the desired unsaturation.

Regardless of which of the saturated acids are used, the degree ofunsaturation necessary to provide crosslinking with the ethylenicallyunsaturated components may be obtained by the addition of any of theabovenamed unsaturated acids or their anhydrides.

The alcohols that can be used are not limited to the dihydric alcoholsas other polyhydric alcohols such as the trihydric and higher polyhydricalcohols may be used. For the polyhydric alcohol component any of thefollowing alcohols may be used: dihydric alcohols such as ethyleneglycol, diethylene glycol, triethylene glycol and propylene glycol; atrihydric alcohol such as glycerol; tetrahydric alcohols such as theerythrilols and pentaerythritols; pentitols which include arabitol,adonitol and xylitol; hexatols including mannitol, sorbitol anddulcitol; heptitols such as persitol and volamitol; or mixtures of anyof the above alcohols may be also employed if desired.

The ethylenically unsaturated component of the polyester resin bindersmay be styrene, vinyl acetate, methyl methacrylate, allyldiglycolcarbonate, diallyl maleate, diallyl glycolate, propylene, butadiene,etc.; as well as derivatives of any of the above substances which arecapable of polymerization with the polyester resin.

The polyester resins suitable as propellant binders and their methods ofpreparation are more fully disclosed in Assignees US. Pat. No.3,031,288, issued Apr. 24, 1962.

Acrylate resin binders within the scope of this invention comprisecopolymers of any two or more reduced oxygen-containing polymerizablemonomers such as alkenoic acids, alkenoic acid esters, dialkenyldiglycolates, dialkylene diglycol bis-(alkenyl carbonate), alkenylphthalates, etc. Examples of reduced oxygencontaining polymerizablemonomers suitable for acrylate propellant binder formation are theacrylates and methacrylates such as methyl methacrylate, methylacrylate, ethyl acrylate, propyl acrylate, butyl acrylate, butylmethacrylate, propyl methacrylate, diethyleneglycol bis-(allylcarbonate), diallyl phthalate, diallyl diglycolate, diallyl maleate anddiallyl fumarate.

Other acrylate binders suitable for use in my invention are prepared bycopolymerizing polymerizable substances containing reduced oxygen in themolecule, such as the nitro and nitroether-substituted alkenoic acidsand esters. Specific examples of nitro-containing monomers whichcopolymerize to form acrylate propellant binders are 2-nitroethylacrylate; the nitrobutyl acrylates; 2,2-dinitropropyl acrylate; 2,2,3,3-tetranitrobutyl acrylate; and 2,2,3,3-tetranitrobutyl methacrylate.

Still other acrylate binders comprise copolymers of any one or more ofthe above-mentioned reduced oxygen-containing monomers and any one ofmore of the above-mentioned monomers containing unreduced oxygen in themolecule. These binders, as well as those acrylate binders referred toabove, and their methods of preparation are more fully described inAssignees copending US. application Ser. No. 321,941, filed Nov. 21,1952, and now abandoned.

Polyurethane resins containing unreduced oxygen are suitable binders forthe propellants of my invention. Such binders can be prepared bycondensing nitrocontaining isocyanates and nitro-containing alcohols, asmore fully disclosed in Assignees copending US. application, Ser. No.728,491, filed Apr. 14, 1958.

Illustrative of other solid propellant binders suitable for use in thenovel propellants of this invention are those disclosed in US. Pat.2,479,828 and British Pat. No. 579,057.

Another class of binder materials useful in the preparation of thepropellants of this invention are the low molecular weightisoolefin-polyolefin copolymers of the type disclosed in Assigneescopending US. application Serial No. 202,351, filed June 8, 1962.

Still other types of binders suitable for use in my novel solidpropellant composition are nitrocelluloseplasticizer binders of the typeprepared by curing mixtures of finely divided nitrocellulose andsuitable plasticizers such as pentaerythritol trinitrate. Binders ofthis type and their methods of preparation are well-known to thoseskilled in the propellant art.

A finely divided nitrocellulose suitable for use in the preparation ofthe subject binders is obtained by first dissolving nitrocellulose,preferably prepared from cotton linters, in a solvent such as an ethylacetate-acetone mixture, an ethyl acetate-ethanol mixture, ornitromethane to form a lacquer. The lacquer is slurried in an aqueousmedium containing a suspending agent such as methyl cellulose incombination with an emulsifier such as turkey red oil and an agent toprevent agglomeration such as, for example, sodium chloride as a resultof which the nitrocellulose precipitates from the solvent and isrecovered as a particulate material having an average particle size ofto 12 microns and an overal particle size range of from about 1 to about35 microns. Finely divided nitrocellulose prepared by theabove-described method is known to those skilled in the art as plastisolgrade nitrocellulose and will be hereinafter referred to as such.Plastisol grade nitrocellulose is readily available on the open market.

Various additives may be employed in preparing the binders of thisinvention. For example, plasticizers, such as, isodecyl pelargonate,polybutene, dioctyl azelate, bis-(2,2-dinitropropyl) formal andbis-(2,2- dinitropropyl) acetal may be utilized. Also catalysts such asferric acetylacetonate and boron trifluoride can be employed if desired.The catalysts can be employed in quantities within the range from meretraces up to amounts equivalent to about one percent by weight of thetotal propellant composition. Normally amounts of from about 0.02 toabout 0.10 percent by weight are employed. Other additives such asantioxidants, wetting agents, anti-foaming agents, etc., can beemployed, if desired, in the formulation of the novel propellants.

Because higher temperatures tend to produce shrinkage and internalstrains, it is preferable to carry out the cure at temperatures in therange of from about to about 180F. Within this range the reaction rateis sufficiently rapid for economical production. Yet the temperature isnot so high as to produce shringkage and internal stresses'which must beavoided at all costs especially in the case of large solid propellantmotors.

Those skilled in the art will appreciate the fact that heating andcooling steps can be incorporated into the propellant processingprocedure to attain optimum operating conditions for producing a givenspecific propellant. Likewise, various techniques which may serve tooptimize the processing procedure or improve the quality of the product,e.g. vacuumizing the mixture during certain phases of the operation, canbe employed if desired. The various processing steps can be carried outwith standard equipment well-known to those skilled in the art. Themixer can be equipped with facilities for heating, cooling, andvacuumizing propellant batches during mixing.

There are many ways of processing the various ingredients within thescope of this invention in the formulation of propellants therefrom, andthese procedures may be readily determined by those skilled in the art,depending on the precise binder, oxidizer, plasticizer, etc., selectedand size of the batch to be prepared.

The propellant binder will be employed in amounts generallycharacteristic of the art and preferably is used in a proportion withinthe range from about 5 to about 55 percent by weight of the totalpropellant composition with the inorganic oxidizing salt, including theporous ammonium salt, being present in an amount within the range fromabout to about 45 percent by weight. The burning rate of the propellantcomposition may be widely varied by adjusting the ratio of the porousammonium salt to the non-porous oxidizing salt but typically the porousammonium salt will be present in a minor portion and generally in theamount from about 7 to 28 percent by weight of the total oxidizing salt.

The following examples are included for purposes of illustrating thenovel oxidizer salt, its process of manufacture and the propellantcomposition of the invention. These examples are intended forillustrative purposes only and should not be construed as limitations ofthe scope of the invention to the particular conditions and embodimentsset forth herein.

Example I Particulate ammonium perchlorate having an average particlediameter of microns is placed in a layer of approximately 0.3 inchesthick and exposed to a temperature of 265C for 30 minutes in a ventedoven. At the end of the heating period, the crystals are decomposed toan extent of about 23 percent by weight. The crystals are then degassedin a partial vacuum for about 24 hours to remove residual acidicdecomposition products. The resulting porous ammonium perchloratecrystals have a typical individual particle density of about 1.5 gramsper cubic centimeter and a bulk density of 0.8 grams per cubiccentimeter.

The porous ammonium perchlorate product is coated with methylziridinyladduct of divinyl benzene. A solution of the methylaziridinyl adduct ofdivinyl benzene in heptane is prepared. The porous ammonium perchlorateis dispersed in a heptane carrier there being 500 grams of the oxidizersalt per one liter of the heptane. The heptane solution of the adduct isadded slowly with vigorous stirring to the oxidizer heptane slurry at60C. The adduct heptane solution is added to the oxidizer slurry in theamount of approximately 40 milliliters per one liter of the oxidizerheptane slurry. Slow stirring is continued for approximately four hoursand then the porous ammonium perchlorate is filtered and dried atapproximately 60C.

TTrIEEIETT aart'iuiaaafilifibmmir perchlorate having anaverage diameterof 200 microns was heated in a layer of about 0.4 inches thick at 265Cin a vented oven for approximately 30 minutes. The crystals were thendegassed in a vacuum for 24 hours. The heating brought about a weightloss of approximately 22 percent, giving a porous ammonium perchloratehaving an individual particle density of approximately 1.5 grams percentimeter and a bulk density of .8 grams per centimeter. The porousammonium perchlorate crystals were coated using the general process ofExample I, employing as the coating material (methylaziridinyl adduct ofdivinyl sulfone) for a portion of the porous product with the balancebeing coated with mehylaziridinyl adduct of divinyl benzene.

Example lll Particulate ammonium perchlorate having an aver-.

ticle density of 1.6 grams per cubic centimeter and a bulk density of0.85 grams per cubic centimeter. The porous ammonium perchlorate productis coated by introducing the particulate material to a bath ofhydroxyterminated polybutadiene which contains, as a catalystapproximately 1 percent normal butyl ferrocene. The polybutadiene israther cumbersome to use because of its high viscosity. Excesspolybutadiene is washed from the coated crystals by employing heptaneand dried at 60C.

Example IV Porous ammonium perchlorate is prepared as in Example III andcoated in a bath of carboxy-terminated polybutadiene containing 1percent normal butyl ferrocene. Polybutadiene is then decanted and thecoated porous ammonium salt washed with hexane. Thereafter the washedmaterial is dried at approximately 50C.

Example V Porous ammonium perchlorate is prepared as in Example andpermitted to stand for fourteen hours in a percent solution of ethyleneimine adduct of divinyl benzene in hexane. The hexane is then decantedand the coated porous ammonium salt washed with additional fresh hexane.The washed coated salt crystals are then dried at approximately 60C.

Example VI Particulate ammonium perchlorate is prepared and coated inaccordance with the process of Example V with the difference being thatthe alkylene imine adduct hexane solution contain a small amount ofhydroxy-terminated polybutadiene, the polybutadiene being present inapproximately percent of the weight of the imine adduct.

Example Vll Porous ammonium nitrate salt having an average diameter ofmicrons is prepared in accordance with the heating process of Example Iand coated with propylene imine adduct of divinyl benzene. A 5 percentsolution of the propylene imine adduct in hexane is added to the porousammonium salt and the mixture tumbled in a rotary dryer at a temperatureof approximately 60C for 18 hours. The hexane is then removed undervacuum to leave a dry coated porous product.

Example VIII The coated porous ammonium chlorate product of the instantexample is prepared in accordance with Example VII with the differencebeing that the coating is formed of the butylene imine adduct of divinylbenzene.

7 ExampleTX A particulate porous ammonium perchlorate salt is preparedby the heating process of Example I and one portion coated with ethyleneimine adduct of divinyl benzene is prepared in accordance with thegeneral procedure of Example 1. Three propellants, all of equal solidscontent are prepared. In propellant A the ammonium perchlorate salt isof the conventional type and present in an amount of 72 percent byweight of the total propellant composition. Propellant B containes 52percent by weight of the normal ammonium perchlorate salt and 20 percentby weight of the porous ammonium perchlorate (uncoated). Propellant Ccontains 52 percent by weight of normal ammonium perchlorate and 20percent by weight of coated porous ammonium perchlorate. The ammoniumperchlorate has an average particle diameter of 600 microns. Each of thethree propellant compositions contains in addition 12 percent aluminumpowder, 5 percent normal butyl ferrocene, and l 1 percent ofaziridiene-cured polybutadiene polymer. The propellant compositions areprepared in accordance with standard mixing practice with, as indicated,in the instance of propellants B and C, a portion of the normal ammoniumperchlorate having substituted therefore the porous product. The threepropellants were tested using a three-inch Crawford bond strand burningtest at 2,000 psi with the following results:

" Table i Propellant A Propellant B, uncoated Propellant C, coated 1.7inch/per second 3.4 inch/per second 6.] inch/per second coated oruncoated, substantially increases the burning rate of the propellant.

Example X In the instant example three different particle sizes ofporous ammonium perchlorate coated with ethylene imine adduct of divinylbenzene are used to demonstrate the effect on burning rate and pressureexponent. The porous ammonium perchlorate is prepared in accordance withthe process of Example I. The three average particle sizes as 600microns, 400 microns, and 180 microns. The porous ammonium perchlorateis incorporated in the formulation of the preceeding example in anamount of 15 percent by weight of the total propellant composition withthe balance of the oxidizing salt being normal ammonium perchlorate. The180 micron porous ammonium perchlorate at the 15 percent level, producesa burning rate of 3.5 inch/per sec ond at 2,000 psi and a pressureexponent of 0.6. The 400 micron average particle size porous ammoniumperchlorate produces a burning rate of 4.1 feet/per second at 2000 psigand a pressure exponent of approximately 0.97. The 600 micron porousammonium perchlorate, at the 15 percent level produces a burning rate of5.0 inches/per second at 2,000 psig and a pressure exponent ofapproximately 1.4. It will be seen that in the instant example, the 180micron size porous ammonium perchlorate with the lower pressure exponentis more desirable for ballistic application.

Example XI In the instant example, the porous ammonium perchloratehaving an average particle diameter of 180 mi crons is coated with 3percent by weight of ethylene imine adduct of divinyl benzene. Theporous product is prepared in accordance with Example II. The porousammonium perchlorate is incorporated in the propellant formulation setforth below in an amount of 15 percent by weight of the totalcomposition. The balance of the ammonium perchlorate solution is normalammonium perchlorate and is provided in two different particle sizes asindicated.

The instant invention contemplates the use of various available binders,plasticizers, catalysts, and other additives in combination with theimproved porous oxidizer. Known propellant mixing techniques may beemployed for the manufacture of the improved propellants with the poroussalt oxidizer being incorporated into the mixture along with the normaloxidizing salt. Typical mixing procedures for the manufacture of metalstaple containing propellants are set forth in copending Assignees U.S.Ser. No. 338,527, filed Jan. 16, 1964. The following compositions arecontemplated as being generally representative of the wide variety offormulations that may advantageously incorporate the porous ammoniumsalt.

Example XII Ingredient Weight Percent Ammonium perchlorate, normal 66.50Porous ammonium perchlorate 15.00 Powdered aluminum 1.00 lsodecylpelargonate 3.50 Lecithin 0.24 Aluminum staple (0.5 X 4.0 X 62 mil) 4.00Copper chromite 1.50 Carboxy-terminated polybutadiene 7.40Tris-(Z-methyl aziridinyl) phosphine oxide 0.86

Example XIII Crawford bomb Ingredient Composition,

Ammonium perchlorate 7-9 microns 39.0 Ammonium perchlorate 125 microns17.0 Porous ammonium perchlorate 180 microns 15.0 Aluminum powder (Pl-)14.0 n-butylferrocene 5.0 Carboxy-terminated polybutadiene (100 eq.)Butylene imine adduct of sebacic acid (95 eq.) tris 1-(2-methy1)aziridinyl phosphene oxide (90 eq.) 10.0

The propellant composition is mixed and cast by Example XIV standardproceduresthe propellant has good flow charlngmdicm Weight puree,acteristics and exhibits the properties set forth in Table 60 llAmmonium perchlorate, normal 61.50 Ammonium perchlorate, porous 20.00Aluminum staple (0.5 X 4.0 X 62 mil) 2.00 Table II Polypropylene glycol9.63 Glycerol monoricinoleate 1.18 Dioctyl azelate 3.62 Burning rate 65Ferric acetylacetonate 0.04 Crawford bomb solid strands. inch/sec at2000 psia 3.5 Phenyl betanaphthylamine 0.20 3KS-500 motors. cxtraplated3.4 Lecithin 0.21 Pressure exponent Tolylene diisocyanate 1.62

3KS-500 motors Example XV Ingredient Weight Percent Ammoniumperchlorate, normal 67.00 Porous ammonium perchlorate 18.00 Lecithin0.20 Phenyl betanaphthylamine 0.20 Polytetramethylene ether glycol 8.95Glycerol monoricinoleate 1.10 Dioctyl azelate 3.00 Ferricacetylacetonate 0.04 Tolylene diisocyanate 1.51

Example XVI It will be understood that various modifications may be madein this invention without departing from the spirit thereof or the scopeof the appended claims.

I claim 1. An improved solid oxidizer comprising a particulate porousammonium inorganic salt characterized by voids throughout and acompatible coating over the exterior surface thereof, said coatingsubstantially sealing 35 the exterior openings of the pores of theammonium salt without filling such pores.

2. An improved solid oxidizer comprising a particulate porous ammoniuminorganic salt characterized by an average individual particle densityof 1.2 to 1.75 grams per cubic centimeter and a compatible coating overthe external surface thereof, said coating substantially sealing theexterior openings of the pores of the ammonium salt without filling suchpores.

3. An oxidizer in accordance with claim 2 wherein the ammonium inorganicsalt is selected from the group consisting of a chromate, permanganate,nitrate, chlorate, and perchlorate.

4. An oxidizer in accordance with claim 2 wherein the ammonium inorganicsalt particles are generally spherical and have an average particlediameter within the range of 5 to 4,000 microns.

5. An oxidizer in accordance with claim 2 wherein the ammonium saltparticles are generally spherical and have an average particle diameterwithin the range of 5 to 250 microns.

6. An oxidizer in accordance with claim 2 wherein the coating is formedof an organic polymeric material.

7. An oxidizer in accordance with claim 6 wherein the oxidizer particlesare coated with an alkylene imine adduct of divinyl benzene.

8. An oxidizer in accordance with claim 2 wherein the coating comprises3 to 8 percent by weight of the ammonium salt.

9. An oxidizer in accordance with claim 2 wherein the inorganic salt isammonium perchlorate and the salt has a bulk density of 0.6 to 1.0 gramsper cubic centimeter.

10. A process of forming an improved solid oxidizer 5 comprising:

effecting a partial decomposition of a particulate inorganic ammoniumsalt through heating to achieve a porous structure; and thereaftercoating the porous particulate ammonium salt, said coating beingcompatible with the ammonium salt and substantially sealing the exterioropenings of the pores of the ammonium salt without filling such pores.11. A process of forming an improved solid oxidizer comprising:

effecting a partial decomposition of a particulate inorganic ammoniumsalt through heating at a temperature within the range of 200 to 350C toachieve a porous structure and a weight loss within 20 the range ofabout 20 to about 35; and

thereafter coating the porous particulate ammonium salts with acompatible organic polymeric material, said coating substantiallysealing the exterior openings of the pores of the ammonium salt withoutfilling such pores.

12; A process in accordance with claim 11 wherein the coating is analkylene imine adduct of divinyl benzene.

13. A process in accordance with claim 12 wherein the alkylene imineadduct is the adduct of ethylene imine and divinyl benzene.

14. A process in accordance with claim 12 wherein the coating isachieved by immersing the porous ammonium salt particles in ahydrocarbon solution of the alkylene imine adduct, whereby the adduct isextracted from the solution onto the porous ammonium salt particles andpolymerized on the surface thereof, said ammonium salt serving tocatalyze the polymerization reaction.

15. A process in accordance with claim 12 wherein the hydrocarbonsolution contains in addition to the alkylene imine adduct anon-volatile, functionalterminated polybutadiene.

16. A process in accordance with claim 11 wherein the ammonium salt isselected from the group consisting of a chromate, permanganate, nitrate,chlorate, and perchlorate.

17. A process in accordance with claim 11 wherein the ammonium salt isammonium perchlorate.

18. A process in accordance with claim 11 wherein the ammonium saltparticles are generally spherical and have an average diameter withinthe range of about 5 to 800 microns.

19. A process in accordance with claim 11 wherein the porous particulateammonium salt prior to coating is degassed in a substantial vacuum toremove residual decomposition products.

20. A process in accordance with claim 11 wherein the porous ammoniumsalt is characterized by an average individual particle density of 1.35to 1.65 per cubic centimeter.

21. A process in accordance with claim 11 wherein the porous ammoniumsalt is characterized by a bulk density of 0.75 to 0.9 grams per cubiccentimeter.

22. A process in accordance with claim 11 wherein the polymeric coatingcomprises 3 to 8 percent by weight of the ammonium salt.

23. A solid propellant composition comprising a cured intimate mixtureof a resin binder and an inorganic particulate oxidizer salt, saidoxidizer salt comprising at least in part a porous ammonium saltcharacterized by voids throughout and present in an amount effective tosignificantly increase the burning rate of the propellant composition.

24. A solid propellant composition in accordance with claim 23 whereinthe porous ammonium salt comprises a minor portion of the oxidizer salt.

25. A propellant composition in accordance with claim 23 wherein theporous ammonium salt comprises by weight about 7 to about 28 percent ofthe total oxidizer salt.

26. A propellant composition in accordance with claim 23 wherein theammonium salt is selected from the group consisting of chromate,permanganate, nitrate, chlorate, and perchlorate.

27. A propellant composition in accordance with claim 23 wherein theporous ammonium salt used in the compound has a bulk density of 0.75 to0.9 grams per cubic centimeter.

28. A solid propellant composition which comprises a cured intimatemixture of resin binder and a particulate ammonium inorganic oxidizersalt, said oxidizer salt comprising at least in part a porous ammoniumsalt characterized by an average individual particle density within therange of 1.35 to 1.65 gams per cubic centimeter, said porous salt beingpresent in an amount effective to significantly increase the burningrate of the propellant composition.

29. A solid propellant composition in accordance with claim 28 whereinthe porous ammonium salt comprises a minor portion by weight of thetotal ammonium salt content.

30. A solid propellant composition in accordance with claim 28 whereinthe porous ammonium salt comprises from about 7 to about 28 percent byweight of the total ammonium salt content of the propellant composition.

31. A propellant composition in accordance with claim 28 wherein theammonium inorganic salt is selected from the group consisting of achromate, permanganate, nitrate, chlorate, and perchlorate.

32. A solid propellant composition in accordance with claim 28 whereinthe porous ammonium salt has a coating over the surface thereof.

33. A solid propellant composition in accordance with claim 32 whereinthe coating on the porous ammonium salt is an organic polymericmaterial.

34. A solid propellant composition in accordance with claim 33 whereinthe polymeric coating is an alkylene imine adduct of divinyl benzene.

35. A solid propellant composition in accordance with claim 28 whereinthe resin binder is the reaction product of a functional-terminatedpolydiolefin and an imine curing agent.

36. A solid propellant composition comprising an inorganic particulateoxidizer salt, said oxidizer salt comprising at least in part a porousammonium inorganic salt characterized by a cubicle crystal structure anda reducing agent comprising a resin binder for reaction with saidoxidizer salt.

37. A solid propellant composition in accordance with claim 36 whereinthe porous ammonium inorganic salt has an average individual particledensity within the range of 1.2 to 1.75 grams per cubic centimeter.

38. A solid propellant composition in accordance with claim 36 whereinthe ammonium inorganic salt is ammonium perchlorate.

39. A solid propellant composition in accordance with claim 36 whereinthe porous ammonium salt has a compatible polymeric coating over thesurface thereof.

2. An improved solid oxidizer comprising a particulate porous ammoniuminorganic salt characterized by an average individual particle densityof 1.2 to 1.75 grams per cubic centimeter and a compatible coating overthe external surface thereof, said coating substantially sealing theexterior openings of the pores of the ammonium salt without filling suchpores.
 3. An oxidizer in accordance with claim 2 wherein the ammoniuminorganic salt is selected from the group consisting of a chromate,permanganate, nitrate, chlorate, and perchlorate.
 4. An oxidizer inaccordance with cLaim 2 wherein the ammonium inorganic salt particlesare generally spherical and have an average particle diameter within therange of 5 to 4,000 microns.
 5. An oxidizer in accordance with claim 2wherein the ammonium salt particles are generally spherical and have anaverage particle diameter within the range of 5 to 250 microns.
 6. Anoxidizer in accordance with claim 2 wherein the coating is formed of anorganic polymeric material.
 7. An oxidizer in accordance with claim 6wherein the oxidizer particles are coated with an alkylene imine adductof divinyl benzene.
 8. An oxidizer in accordance with claim 2 whereinthe coating comprises 3 to 8 percent by weight of the ammonium salt. 9.An oxidizer in accordance with claim 2 wherein the inorganic salt isammonium perchlorate and the salt has a bulk density of 0.6 to 1.0 gramsper cubic centimeter.
 10. A process of forming an improved solidoxidizer comprising: effecting a partial decomposition of a particulateinorganic ammonium salt through heating to achieve a porous structure;and thereafter coating the porous particulate ammonium salt, saidcoating being compatible with the ammonium salt and substantiallysealing the exterior openings of the pores of the ammonium salt withoutfilling such pores.
 11. A process of forming an improved solid oxidizercomprising: effecting a partial decomposition of a particulate inorganicammonium salt through heating at a temperature within the range of 200*to 350*C to achieve a porous structure and a weight loss within therange of about 20 to about 35; and thereafter coating the porousparticulate ammonium salts with a compatible organic polymeric material,said coating substantially sealing the exterior openings of the pores ofthe ammonium salt without filling such pores.
 12. A process inaccordance with claim 11 wherein the coating is an alkylene imine adductof divinyl benzene.
 13. A process in accordance with claim 12 whereinthe alkylene imine adduct is the adduct of ethylene imine and divinylbenzene.
 14. A process in accordance with claim 12 wherein the coatingis achieved by immersing the porous ammonium salt particles in ahydrocarbon solution of the alkylene imine adduct, whereby the adduct isextracted from the solution onto the porous ammonium salt particles andpolymerized on the surface thereof, said ammonium salt serving tocatalyze the polymerization reaction.
 15. A process in accordance withclaim 12 wherein the hydrocarbon solution contains in addition to thealkylene imine adduct a non-volatile, functional-terminatedpolybutadiene.
 16. A process in accordance with claim 11 wherein theammonium salt is selected from the group consisting of a chromate,permanganate, nitrate, chlorate, and perchlorate.
 17. A process inaccordance with claim 11 wherein the ammonium salt is ammoniumperchlorate.
 18. A process in accordance with claim 11 wherein theammonium salt particles are generally spherical and have an averagediameter within the range of about 5 to 800 microns.
 19. A process inaccordance with claim 11 wherein the porous particulate ammonium saltprior to coating is degassed in a substantial vacuum to remove residualdecomposition products.
 20. A process in accordance with claim 11wherein the porous ammonium salt is characterized by an averageindividual particle density of 1.35 to 1.65 per cubic centimeter.
 21. Aprocess in accordance with claim 11 wherein the porous ammonium salt ischaracterized by a bulk density of 0.75 to 0.9 grams per cubiccentimeter.
 22. A process in accordance with claim 11 wherein thepolymeric coating comprises 3 to 8 percent by weight of the ammoniumsalt.
 23. A solid propellant composition comprising a cured intimatemixture of a resin binder and an inorganic particulate oxidizer salt,said oxidizer salt comprising At least in part a porous ammonium saltcharacterized by voids throughout and present in an amount effective tosignificantly increase the burning rate of the propellant composition.24. A solid propellant composition in accordance with claim 23 whereinthe porous ammonium salt comprises a minor portion of the oxidizer salt.25. A propellant composition in accordance with claim 23 wherein theporous ammonium salt comprises by weight about 7 to about 28 percent ofthe total oxidizer salt.
 26. A propellant composition in accordance withclaim 23 wherein the ammonium salt is selected from the group consistingof chromate, permanganate, nitrate, chlorate, and perchlorate.
 27. Apropellant composition in accordance with claim 23 wherein the porousammonium salt used in the compound has a bulk density of 0.75 to 0.9grams per cubic centimeter.
 28. A solid propellant composition whichcomprises a cured intimate mixture of resin binder and a particulateammonium inorganic oxidizer salt, said oxidizer salt comprising at leastin part a porous ammonium salt characterized by an average individualparticle density within the range of 1.35 to 1.65 gams per cubiccentimeter, said porous salt being present in an amount effective tosignificantly increase the burning rate of the propellant composition.29. A solid propellant composition in accordance with claim 28 whereinthe porous ammonium salt comprises a minor portion by weight of thetotal ammonium salt content.
 30. A solid propellant composition inaccordance with claim 28 wherein the porous ammonium salt comprises fromabout 7 to about 28 percent by weight of the total ammonium salt contentof the propellant composition.
 31. A propellant composition inaccordance with claim 28 wherein the ammonium inorganic salt is selectedfrom the group consisting of a chromate, permanganate, nitrate,chlorate, and perchlorate.
 32. A solid propellant composition inaccordance with claim 28 wherein the porous ammonium salt has a coatingover the surface thereof.
 33. A solid propellant composition inaccordance with claim 32 wherein the coating on the porous ammonium saltis an organic polymeric material.
 34. A solid propellant composition inaccordance with claim 33 wherein the polymeric coating is an alkyleneimine adduct of divinyl benzene.
 35. A solid propellant composition inaccordance with claim 28 wherein the resin binder is the reactionproduct of a functional-terminated polydiolefin and an imine curingagent.
 36. A solid propellant composition comprising an inorganicparticulate oxidizer salt, said oxidizer salt comprising at least inpart a porous ammonium inorganic salt characterized by a cubicle crystalstructure and a reducing agent comprising a resin binder for reactionwith said oxidizer salt.
 37. A solid propellant composition inaccordance with claim 36 wherein the porous ammonium inorganic salt hasan average individual particle density within the range of 1.2 to 1.75grams per cubic centimeter.
 38. A solid propellant composition inaccordance with claim 36 wherein the ammonium inorganic salt is ammoniumperchlorate.
 39. A solid propellant composition in accordance with claim36 wherein the porous ammonium salt has a compatible polymeric coatingover the surface thereof.